The following abbreviations which may be found in the specification and/or the drawing figures are defined as follows:
3GPP 3rd Generation Partnership Project
CDMA Code Division Multiple Access
CSG Closed Subscriber Group
eNB evolved Node B
EHPLMN equivalent HPLMN
E-UTRAN Evolved Universal Terrestrial Radio Access Network
GERAN GSM EDGE Radio Access Network
GSM Global Systems for Mobile communications
GPRS General Packet Radio Service
HPLMN home PLMN
LTE Long Term Evolution
MCC Mobile Country Code
MNC Mobile Network Code
MS mobile station
PLMN public land mobile network
RAT radio access technology
RPLMN registered PLMN
UMTS Universal Mobile Telecommunications System
UTRAN Universal Terrestrial Radio Access Network
Use has been made of small cell wireless access technology, in which a small cell is serviced by a small, low-power cellular base station. The term “femtocell” is often used for such small cells, though other terminology is also used. These are typically designed for use in a home, restaurant or small business or the like, and may have a range of the order of 10 m to 100 m or so (though other ranges are possible). Such small cells may provide service only for a limited number of specific users or subscribers, and in such a case may be referred to as a Closed Subscriber Group or CSG cell. Any given CSG may include a group of cells or a single cell. CSGs may allow traffic access for non-subscribers for emergency calls or routine, non-emergency access. The small cell (i.e. its base station) is typically ultimately connected to a core network. That core network may be a core network of a public land mobile network (PLMN) which comprises the core network and a radio access network that provides wireless access to the core network. The radio access network of the PLMN may be a “large” or “macro” cell, using for example a high power cellular base station or the like.
However, there are a number of problems associated with such small cells, particularly CSG cells, especially when a particular wireless device or “user equipment” that was using a CSG cell attempts to start using a macro cell.